This invention relates to a method for recording and reproducing digital data. More particularly, it relates to a method for transmitting digital data, such as digital audio signals recorded simultaneously with video signals.
As the method for recording digital audio signals, there is so far known a method shown in the Japanese Patent Applications laid open Nos. 36410/1982 and 104714/1984 filed in the name of the present Assignee, wherein digital signals sampled at the sampling frequencies of 32 kHz, 44.1 kHz and 48 kHz so that each sample is formed by 16 bits, are formed on a plurality of digital audio tracks, two analog audio tracks and each one time code track and control track, these tracks extending along the tape running direction.
However, since the consumer appliances also make use of the similar sampling frequencies, with each sample including 16 bits, there is practically no difference in the performance between these consumer appliances and professional appliances.
These professional appliances are used in general for forming software programs for these consumer appliances, as an example. In the course of the program formation, it becomes necessary to edit recorded audio signals. However, the audio signals are usually deteriorated in sound quality during such editing. In this consideration, there is a demand in the professional appliances for expanding each sample data from 16 bits to 20 bits, in order to comply with future improvement in the performance of AD converters and to cope with deterioration in the sound quality at the time of editing. Nowadays, devices such as AD converters adapted in this manner have become more and more available.
In digital video tape recorders (VTRs) adapted to record and reproduce digital video signals, audio signals are recorded in the digital form. The Japanese Patent Application laid open No. 199179/1987, assigned to the present assignee, disclosed a VTR in which television signals are recorded in the digital form. Although this prior art technique shows an example of three kinds of audio signal recording modes, it is also contemplated to make digital recording of audio signals by stationary heads, in addition to these modes, in consideration that the tape running speed of the VTR adapted to record television signals is relatively high and amounts approximately to 805 mm/sec. In such case, it is similarly preferred that each sample data be expanded from 16 bits to 20 bits.
For implementing such bit expansion, since it is preferred not to abandon the basic 16-bit pattern, the 20 bits of one sample data can be divided into, for example, 16 bits and 4 bits, in order to assure compatibility with the original 16-bit data format.
The Japanese Patent Application laid open No. 30108/1982, similarly assigned to the present Assignee, discloses a technique of expanding the 14-bit-per-word data format for audio PCM recording by the consumer VTR into a 14-bit-per-word data format. In this technique, when the data format in which six sample data words having a word length of 14 bits, P and Q parities and CRCC (Cyclic Redundancy Check Code) of 16 bits are arranged in one horizontal period (1H) of the standard television signals of the NTSC system, is to be expanded to 16-bit words, the 14 bits of each of the seven words of the sample data and the P parity are arrayed at the original word positions, while the remaining two bits of these seven words are arrayed in the same sequence to form a 14-bit data which are arrayed at the word position of the Q-parity.
When the 14 bit portion and the remaining two bit portion are collectively arrayed in one block corresponding to each horizontal period, problems are presented in that error correction cannot be made in association with criticality of these portions.